Uncertainty in seabed properties can lead to substantial uncertainties in acoustic propagation, of order tens of dBs. During this project, substantial progress was made in 1) quantifying seabed uncertainties, by developing an advanced seabed measurement technique and powerful commensurate methods to estimate the uncertainties and 2) predicting the effect of those effects on propagation by devel...

When the gas hydrates dissociate, the mechanical properties of sediments will change, which may cause the deformation of the seabed. Such incidence will directly affect the stability of the undersea device. Under the consideration of seepage-stress coupling, this paper analyzed the deformation of seabed using finite element method. Duncan Chang’s E-B constitutive model code was written, the imp...

Seabed classification is the important part of current coastal research because it characterizes the seabed and its habitats. Seabed characterization makes the link between the classified area and the physical, geological, chemical or biological properties of seabed. This paper addresses the possibilities of the use of airborne hyperspectral sensing with a CASI-1500 sensor to map the seabed cov...

hysteretic dampers as the most practical passive control methods have improved the seismic performance of steel structures through energy dissipation induced by large inelastic deformations. among them in this paper, kbf (knee braced frames), a special form of braced frames having a diagonal brace connected to a knee element instead of beam-column joint, is investigated. in such systems, the kn...

The development of seabed trench by the steel catenary riser (SCR) touch-down zone (TDZ) in its early life can be caused installation loads, direct hydrodynamic and vessel first second-order motions on SCR. This paper presents a numerical technique which pre-trench initiated for fatigue response calculations during SCR detailed design analysis. Examples are presented to demonstrate new approach...

Spatially continuous predictions of seabed hardness are important baseline environmental information for sustainable management of Australia's marine jurisdiction. Seabed hardness is often inferred from multibeam backscatter data with unknown accuracy and can be inferred from underwater video footage at limited locations. In this study, we classified the seabed into four classes based on two ne...

Piezoelectric, magnetostrictive, and shape memory alloy actuators are gaining importance in high-frequency precision applications constrained by space. Their intrinsic hysteretic behavior makes control difficult. The Prandtl–Ishlinskii (PI) operator can model hysteresis well, albeit a major inadequacy: the inverse operator does not exist when the hysteretic curve gradient is not positive defini...

With the increasing popularity of actuators involving smart materials like piezoelectric, control of such materials becomes important. The existence of the inherent hysteretic behavior hinders the tracking accuracy of the actuators. To make matters worse, the hysteretic behavior changes with rate. One of the suggested ways is to have a feedforward controller to linearize the relationship betwee...